WIP: Eliminate event.target() usage from TrayEventFilter

ui/views/mus/window_manager_connection.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_MUS_WINDOW_MANAGER_CONNECTION_H_
 #define UI_VIEWS_MUS_WINDOW_MANAGER_CONNECTION_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 57 matching lines @@
   WindowManagerConnection(shell::Connector* connector,
                           const shell::Identity& identity);
   ~WindowManagerConnection() override;
 
   // Returns true if there is one or more pointer watchers for this client.
   bool HasPointerWatcher();
 
   // mus::WindowTreeDelegate:
   void OnEmbed(mus::Window* root) override;
   void OnConnectionLost(mus::WindowTreeConnection* connection) override;
-  void OnEventObserved(const ui::Event& event) override;
+  void OnEventObserved(const ui::Event& event, mus::Window* target) override;
 
   // ScreenMusDelegate:
   void OnWindowManagerFrameValuesChanged() override;
   gfx::Point GetCursorScreenPoint() override;
 
   shell::Connector* connector_;
   shell::Identity identity_;
   std::unique_ptr<ScreenMus> screen_;
   std::unique_ptr<mus::WindowTreeConnection> window_tree_connection_;
   // Must be empty on destruction.
   base::ObserverList<PointerWatcher, true> pointer_watchers_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowManagerConnection);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_MUS_WINDOW_MANAGER_CONNECTION_H_